12-60mm zoom locked up

My 12-60mm has a screw loose I fear. It won't zoom the whole rage, and rattles when shaken. Shaking it initially changed where on the range it locked, but it seems to be stuck at the long end now. I took the back plate off to check if the screw fell out from there, but it seems to be buried deep in the helical outer part. I've read of people worried about clunks in the zoom range, but not locking against a hard stop before. Anyone had the same?

Looks like a trip to Oly. Anyone know the standard repair fee on the 12-60 in the UK? I might try Luton Cameras to see if they do that sort of thing first, though Oly would give it a complete overhaul I guess.